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quick and easy pcv check?

eurocars

5/17/15 - Never forget
Location
Indianapolis
Car(s)
2006 GTI
Taking off the oil cap while idling should cause the engine to run like shit, but just because it does run like shit does not mean the pcv valve is ok. The best check is remove airbox and pull hose off of manifold that goes to pcv and try to blow through the valve. You should NOT be able to blow through the valve.

..in one direction
 

soze

Go Kart Champion
Location
Orange County, CA
Car(s)
Something Else
same way to test for the TSI?
 

Renagade

I am the Evil Bastard!!
after the pcv fix, i removed the cap while idling. ran fine.
 

delavmkv

Passed Driver's Ed
Location
Vancouver, WA
Car(s)
2008 GLI
Hey! This is my first post on golfmkv, but I just wanted to say that I really enjoy the board (especially compared to vortex). Here is my VW:



To clarify - a properly functioning PCV valve should allow a user to remove the oilcap without affecting the idle? There seems to be a fair amount of conflicting information out there!

Thanks
 
Location
Green Bay, WI
Car(s)
2008 GTI
Hey! This is my first post on golfmkv, but I just wanted to say that I really enjoy the board (especially compared to vortex). Here is my VW:



To clarify - a properly functioning PCV valve should allow a user to remove the oilcap without affecting the idle? There seems to be a fair amount of conflicting information out there!

Thanks

I agree. I do not think this was ever definitively answered.

Feel free to pop by here and say hi! And welcome to my favorite place to be :happyanim:

http://www.golfmkv.com/forums/showthread.php?t=26&highlight=introduce&page=211
 

yeahforbes

Ready to race!
Location
NJ
Car(s)
2017 Golf R DSG
This thread is fairly old, but I'm reviving it because I'm looking to check my pcv and ended up here, yet the thread ended with a distinct lack of information about whether the car is supposed to idle better or worse when the oil filler cap (or dipstick) is removed.

Does anyone know for sure, and is this a guaranteed way to diagnose that a pcv is either good or bad based on the results of doing this? Or should the oil cap / dipstick test be completely ignored and we should only use the blow-into-the-hose test?

EDIT: My engine idles rough when pulling the dipstick, and I can't blow into the hose. I think it's good...
 
Last edited:

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
If equipped with a PCV delete, removing the filler cap will change nothing as the tube to the intake manifold was deleted when a PCV delete or a catch-can was installed.

If it is still PCV equipped, removing the oil filler cap, or pulling the dipstick out a bit, should make it run rough at idle because you've introduced an air inlet leak. Meaning the MAF now reads much less air. Blowing into the PCV-to-manifold tube when disconnected (where circled), only tests the check valve (at the arrow) inside the PCV is containing boost in the manifold when boost is present. If this check valve is failing to contain boost...it will still run rough when the filler cap is removed.
pcv boost check 1.png


There are still two more valves within the PCV system. The large diaphragm inside the large disc can be torn. Its cap can be removed for access to inspect it. But the cap is delicate and can break or chip while attempting to remove it. Then there is the rear recycling check valve. It is either mounted inside the Rev.-R PCV or mounted in the rear vent tube if using the Rev.-P PCV. The recycling check valve opens to the turbo inlet when there is positive crankcase pressure and closes when crankcase vacuum is present.
 
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